It's a derogatory term to refer to a White guy or girl. Because White people are hairy like monkeys.
The Japanese use the term shiro-saru, which translates to Albino monkey to refer to a White American or European. Native Americans, Latinos, and Asians use the term Albino monkey in their own languages.

Native American - look at that ugly Albino monkey.
Asian - Look at that Albino monkey eating bananas.
Japanese - That Albino monkey shiro-saru can sure climbed a tree.